1. Take him out the tank with half the water from the tank (I'm going to use his old petsmart cup to temporarily hold him)
2. Empty the tank, refill it and add the declorinator.
* 3. Let the water sit for about 1 minute then start floating fish's cup with 1/2 old water 1/2 new water
4. 15 min later dump out 75% of the water and add new water.
5. 15 minutes later the temp should be the same in both the cup and the tank and it is now safe to pour fish into the water.
You got it mostly right. :) Everyone does it a different amount of time but I find this to be the most effective. Some people just float 15 min to get the temperature right and dump fish in but ONLY if the water source of the new water is the same of the old water. But I still recommend acclimating every time.